1. Field of the Invention
The invention relates to the field of environmental air management and control systems. More particularly, the invention relates to systems which sample indoor environmental air to make periodic or continuous quality measurements, including for example chemical composition, temperature, and pressure.
2. Related Art
Over the decades of the 70""s, the 80""s and the 90""s, people have become much more energy-conscious than ever before. Among other things, this has driven the construction industry towards building structures which are far xe2x80x9ctighterxe2x80x9d than their predecessors, with respect to air leakage. Building designs are carefully made to provide occupants with precisely metered exchange between the indoor and outdoor air. The exchange between indoor and outdoor air is selected to provide a healthy quality of indoor air, with a minimum of energy usage for heating or cooling the outdoor air introduced. However, inevitably the tradeoff sometimes results in unacceptable indoor air quality. Moreover, the use of new building materials having many superior and desirable properties in both renovations of old buildings and new construction sometimes aggravates the air quality problems because they outgas undesirable substances. Since indoor air quality problems have a direct effect on the health of occupants of a building, there is now great interest in determining the air quality in various structures.
In laboratory settings, including chemical laboratories, biotechnological laboratories and semiconductor fabrication laboratories for example, many harmful chemicals are used. Fume hoods are used to confine and remove any harmful chemicals which may be introduced into the room by an experiment or process. Fume hoods are specially designed, confined structures in which an air flow is set up to exhaust away from a human operator any harmful substances introduced into the air. Proper operation of a fume hood requires that the air flow setting be appropriate for various parameters, including the size of the opening through which the operator may need to manipulate equipment in the hood, the supply of makeup air into the laboratory room in which the fume hood is located, and the type of materials and experiments being performed in the hood, for example. Fume hoods therefore typically include a controller which responds to various settings and determines a proper air flow through the hood. The controller then sets appropriate valve positions, fan settings, etc. to achieve the desired air flow setting. However, if a human operator improperly sets a parameter in the controller, or if the controller or a controlled element fails, then the proper air flow may not be set, resulting in a xe2x80x9cspillxe2x80x9d of some substance from inside the fume hood into the indoor air of the human operator. Such a spill may have a minor effect on indoor air quality or may be extremely hazardous, depending on the nature of the substance spilled and the size of the spill. Detecting spills quickly is important both for evacuating areas in a timely manner if required, and for correcting the problem which caused the spill in the first place.
Both of the areas of concern discussed above have resulted in a great deal of work in the area of measuring indoor air quality. A wide variety of sensors are available, for measuring temperature, humidity, CO2, CO, volatile organic compounds (VOCs), smoke, various other chemical contaminants, particulate levels, dust, animal odors sch as caused by rat urine proteins (RUPs), etc.
In one prior approach, shown in FIG. 10, to the problem of measuring indoor air quality, remote sensors for each of the substances or parameters of indoor air quality desired to be measured are placed at each site of interest within a structure. In one variation, the sensors may simply record their measurements locally, for later collection while in another variation they may be connected through electronic wiring to a central data collection system.
One major problem with local data collection is that it is useless for real time control, since the data is not available, except when collected. With a remote sensor system having central data collection, the data is available whenever the central system polls each particular sensor. However, another major problem with remote sensor systems is that they require the use of a multiplicity of expensive sensors at the individual sites to be measured. The expense is very high and the system is fairly inflexible. If a new parameter needs to be measured throughout a structure, a multiplicity of new sensors need to be installed at all the relevant sites.
Another approach to the problem, shown in FIG. 11, is a multiple point, sequenced system including a central computerized sensing system having a plurality of input ports connected via hollow tubes to each room of interest. A vacuum system is used to draw air samples through the tubes from each room down to the central sensing system, where a single sensor suite sequentially performs measurements on each of the air samples obtained. This system is far less expensive than those described above because it only uses one set of sensors. It is also far more flexible, in one sense, because there is only one sensor suite to be changed, if the measurements desired should change.
However, this approach is still relatively inflexible and expensive to install because of the large bundle of individual sensing tubes which must be run from the central sensing location to each site from which a sample is desired. There is also a cost associated with unused capacity held in reserve to receive additional sensing tubes at the central computerized sensing system, should potential changes to the structure requiring additional sampling sites be implemented. Such changes are common in both office and laboratory settings, where space is frequently divided and consolidated as the goals and tasks of organizations change.
Yet another conventional approach to this problem is a centralized sensing system having a single sample tube. The sample tube is snaked through the building to each space where it is desired to take an air sample. A hole is made in the sample tube at each point where an air sample is desired to be drawn from. However, such a system is extremely limited since the system makes a single, xe2x80x9cmixedxe2x80x9d measurement of the air drawn in through the holes in the sample tube. In other words, this system uses the sample tube as a mixing chamber in which the air drawn in through the holes is blended or homogenized into a single sample. This system lacks the capability to make individual measurements of the air drawn in through each separate hole. Rather, averaged measurements of desired parameters are made.
Therefore, it is desired to provide an air sampling system which solves the above noted problems. It is desired to provide an air sampling system which provides data to a central system, whereby building elements affecting air flow near a sampling site may be controlled in response to changes in local air quality. It is desired to provide an air sampling system in which installation costs are relatively low and flexibility is relatively high.
Embodiments of the present invention can be installed in parallel with the electrical and pneumatic networks conventionally used in modern construction. Hence, installation cost is kept low. In many installations, Phoenix Controls Corporation electronically controlled valves or other electronically controlled valves or airflow controls will be used throughout. In such cases, an embodiment of the invention may use the valve sites as junction sites. Some inexpensive system components may even be preinstalled at other junction sites in anticipation of future expansion. By so doing, great flexibility is achieved at minimal cost.
Various aspects of the present invention described below address these concerns and such others as will become evident to those skilled in this art.
According to one aspect of the invention, there is provided a networked air measurement system including a sensor capable of measuring a characteristic of an air sample. Suitable sensors typically have an air inlet port through which an air sample, comprising a small quantity of air to be measured may enter the sensor and an exhaust port through which the air sample may exit the sensor. The characteristics which such sensors measure may include, but are not limited to, temperature, humidity, pressure, particulate levels and contaminant levels (e.g., CO, CO2, VOCs, RUPs, etc.) A backbone tube is in communication with the air inlet port of the sensor. The backbone tube may be a length of pneumatic tubing, for example of a plastic or metal. A plurality of air intake valves in communication with the backbone tube admit air into the backbone tube. The air intake valves may be any suitable remotely controlled intake valves. They may be solenoid or poppet valves, pneumatic valves, gate valves, butterfly valves or other substantially two-position valves, for example. An air flow induction device in communication with air in the system moves air from the plurality of air intake valves through the backbone tube, to the sensor. The air flow induction device may be an exhaust blower, air compressor or vacuum pump connected to produce a low pressure at the exhaust port of the sensor, for example. Other air induction devices can be used, such as a ducted blower connected between the backbone tube and the inlet port of the sensor. A controller connected to the sensor and to each air intake valve executes a control sequence which opens and closes air intake valves to admit air and form air samples communicated to the sensor. A suitable controller may be a personal computer or microprocessor unit executing special-purpose software, for example. This basic system is subject to numerous useful variations.
Enhancements to the tubing portion of the system are possible. For example, the system may further include a plurality of branch tubes connected between the backbone tube and each one of the plurality of air intake valves, bringing each one of the plurality of air intake valves into communication with the backbone tube. Further enhancements to the controller are possible. For example, the controller may execute a control sequence in which each one of the plurality of air intake valves is opened and closed at individually defined times which result in a separate air sample from each one of the plurality of air intake valves being communicated through the backbone tube to the sensor. In addition, the controller may execute a control sequence in which predefined groups of air intake valves are opened and closed substantially in unison, a measurement is made by the sensor, and each one of the plurality of air intake valves is opened and closed at individually defined times only when the measurement meets predefined criteria. In another variation of the controller, a measurement may be made by the sensor and the controller may monitor the measurement to determine when a stable air sample is achieved. In yet another variation on the controller, the controller may include a timer which is monitored by the controller to determine that a stable air sample is achieved after a predetermined interval, the predetermined interval individually defined for each one of the plurality of air intake valves. Finally, the controller may monitor a measurement made by the sensor after the predetermined interval, the controller determining from the measurement that a stable air sample is achieved.
In other variations the air samples taken may be directed through the system. For example, there may be an air sample router connected between the backbone tube and a group of the plurality of branch tubes. The air sample router and the air flow induction device may then be controlled by the controller to route air admitted through one of the plurality of air intake valves to a destination. In a further variation, there may be a second sensor in communication with the backbone tube through a branch tube and the air sample router, wherein the destination of the air admitted through one of the plurality of air intake valves is the second sensor.
Some variations on the air intake valves are contemplated. An air intake valve may provide an average sample from an air flow. Such a valve may include an high pressure inlet port; an averaging chamber in communication with the high-pressure inlet port, air admitted through the inlet port over a time interval being mingled in the averaging chamber; a low pressure outlet port in communication with the averaging chamber, air being exhausted from the averaging chamber through the low-pressure outlet port; and a solenoid valve in communication with the averaging chamber and the backbone tube, through which air from the averaging chamber is admitted to the backbone tube. In this type of valve, the inlet port and the outlet port may be disposed on a high-pressure side and a low-pressure side respectively of an air flow control device, such as a room exhaust valve or a room make-up air supply valve. Alternatively, the inlet port may be disposed in a room air space when a room exhaust valve is used.
According to another aspect of the invention, a method of measuring air quality at a plurality of sites, may include the steps of: drawing a plurality of air samples from the plurality of sites into a common inlet tube; moving the plurality of air samples through the common inlet tube from the plurality of sites to a common sensor at a fixed location, substantially without mixing the air samples with each other due to time sequencing of the samples; and measuring a parameter of each of the plurality of separate air samples. The step of drawing may further include drawing one air sample over a period of time, whereby the one air sample averages the parameter over the period of time during which the air sample is drawn.
Numerous other variations and combinations contemplated by the inventor as within the spirit and scope of the invention will now be apparent to those skilled in the art.